In this photo provided by Frank Caprio, performers hang during an aerial hair-hanging stunt at the Ringling Brothers and Barnum and Bailey Circus, on Friday in Providence, R.I. / Frank Caprio, AP

by Jolie Lee, USA TODAY Network

by Jolie Lee, USA TODAY Network

The eight performers who plunged to the ground Sunday during a Ringling Bros. and Barnum & Bailey act were hanging from their hair literally.

The incident sheds light on a circus act that goes back centuries and is rare even among aerial performers.

In this type of act, performers are indeed hanging from their hair.

Hair, it turns out, is stronger than you probably think.

"A single strand of hair is about as strong as an equivalent-sized copper wire," said Steven Santos, spokesman for Simply Circus, a center that teaches hair hang and other circus arts in Newton, Mass., in an interview with USA TODAY Network.

Depending on the hair type, a single strand of hair can hold 100 grams of weight, Santos said.

But, in practice, the scalp would not be able to withstand anywhere close to that much weight, Santos said.

A hair aerialist's hair is braided in special ways to withstand the weight that is being supported. Braiding techniques often stay in the family, passed down from generation to generation as "family secrets," according to Santos.

"There are so many really specific techniques that go into making these braids correct that it's next to impossible to learn without spending a long time under somebody else," Santos said.

If hair hanging is done incorrectly, it can "literally tear the scalp off," he said.

Even done correctly, performing a hair hang hurts. Acts typically last about 5 minutes, and 15 minutes is considered a long act, he said.

"It's painful, but it's something your body adjusts to," Santos said.

The Ringling show has long featured a hair hang act, and the show expanded to eight hair hang performers starting in January. Prior to that, only two or three hair aerialists performed at a time, said Stephen Payne, spokesman for Feld Entertainment, parent company of Ringling Bros.

"Audiences love it," Payne said. "It's a beautiful act, and these are very talented ladies."